This proposal is to complete the feasibility prototype of an adjustable systemic-pulmonary artery (SPA) shunt. Children with single ventricle physiology (SVP) and reduced pulmonary blood flow (PBF) are palliated with an SPA shunt until approximately 6 months of age. Current shunts are made from simple (unadjustable) polytetrafluoroethylene (PTFE) vascular grafts. The amount of blood which flows through the tube into the lungs versus the systemic circulation is critical, yet there is no way to reliably balance the flow between the circuits. In order to address this problem, our laboratory is in the process of developing an adjustable SPA shunt. Proof-of-concept prototypes have been created of the four component parts: the resistor, the torque transmission cable (TTC), torque producing unit (TPU), and the controller wand (CW). The CW is an electromagnet which provides torque from outside the patient to the TPU, which is implanted inside the chest. The TPU turns the TTC which terminates in a screw-plunger mechanism on the outside of the PTFE graft. The screw-plunger changes the diameter and resistance of the graft. The TPU has been constructed as twice normal size during the proof-of-concept stage. The project has 4specific aims: 1) complete the refined prototype by miniaturizing the TPU and adding a ball-and-socket joint to the screw-plunger mechanism; 2) individually test the torque production of the TPU versus the torque requirements of the screw-plunger to make certain the torque production is adequate; 3) test the entire device on an established pressure-flow system to demonstrate its effectiveness at controlling flow in an in vitro model; 4) perform preliminary fatigue testing to verify the durability of the device.